A massive contingent of area firefighters converged on the mixed-use Piaget Avenue building after the blaze broke out in a second-floor apartment and then spread to the cockloft.
No serious injuries were immediately reported, nor was the cause of the fire immediately known.
The building houses two restaurants -- Aurora Ristorante and Zen Sushi -- two other businesses (Smoke Shop and Epic Cuts) and four upstairs apartments.
Firefighters almost immediately went to an exterior attack after arriving around 2:30 p.m. An hour and a half in, the roof collapsed.
They continued to pour water on the blaze as the number of alarms reached five by early evening.
Nearby homes and businesses were evacuated as a precaution.
The building will have to be bulldozed, responders at the scene said.
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